1. Field of the Invention
Various embodiments of the invention relate to haptic systems and, more particularly, to systems, devices, and methods to transmit pressure waves, based on input electrical signals, through a sealed capsule filled with non-rigid matter, so as to produce haptic actuation of a surface.
2. Description of Related Art
Haptics is the science and technology of simulating felt sensations through a device for human contact. Haptics, used in conjunction with computational systems, promises to provide “for the sense of touch what computer graphics does for vision.” (Robles-De-La-Torre, G. “Virtual Reality: Touch/Haptics.” In Goldstein B (Ed.), Encyclopedia of Perception, Vol. 2, pp. 1036-1038, Sage Publications, Thousand Oaks, Calif. (2009)). Current technologies fall along a spectrum of achieving this promise.
The actuation mechanism most commonly in use in contemporary consumer haptics, such as those used in smart phones and vibrating videogame controllers, is the vibrating motor, or vibromotor. Vibromotors consist of a small rotary motor with an unbalanced mass. When supported and rotated within a rigid housing, vibromotors send vibration throughout the entire device. Vibromotors have certain disadvantages. They provide a low resolution, coarse, “buzzy” sensation often accompanied by a buzzing sound. They have limited configurability, meaning that the types of effects that they can produce are limited. They vibrate the entire housing of the device, and this vibration is non-localizable to a specific spot. Vibromotors do not translate well to soft surfaces, flexible surfaces, and textiles because of the need for a rigid housing to support the eccentric motor and carry the vibration.
Ceramic piezoelectric actuators will either vibrate or change shape when a voltage is applied. These piezoelectric elements have a slim profile and faster response time than vibromotors. They are more precisely controllable, thus producing higher resolution haptics and a larger library of effects. However, they operate at voltages in the one hundred to two hundred volts range and require more complex driver systems than vibromotors or other electromechanical components. Further, currently available materials for piezoelectric actuators are too brittle to be placed in soft or flexible surfaces. (Levin, M. and Woo, A. “Tactile-Feedback Solutions for an Enhanced User Experience,” In Information Display, Volume 25, issue 10, pages 18-21.) Piezoelectric components may be coupled to the housing of a device to vibrate the housing, but the resulting vibration is not localized to a limited spot along the housing.
Dielectric electroactive polymers use the capacitance between two electrodes placed around an elastomer film, such that when a voltage is applied, the electrodes compress the film, thus elongating it. These also require high voltages, in the thirty megavolt/meter range, making them impractical for portable applications.
Other haptics technologies include mechanical force feedback devices and inertial force feedback devices, often in stylus or computer mouse form. These devices are often used in conjunction with graphics on a computer screen to simulate the haptic sensation of varying mechanical resistance when a cursor or other pointer on the screen encounters a graphically differentiated area. These technologies have not become portable beyond desktop-scale or laptop-scale computing systems.
Another class of haptic technologies uses differences in charge between an electrical field on a computer screen and a human appendage in contact with the screen to create felt sensations. For example, an invention called TeslaTouch, sponsored by Disney Research, can create a palpable charge difference between a human finger and the computer screen. This charge difference is configured to simulate various texture sensations by creating slight mechanical tugs on the skin. In this case, one part of the human body, such as a thumb or part of the palm, must be in contact with a conducting strip that provides a ground voltage, and the tactile sensations are felt when the finger is in motion.
None of the above mentioned technologies are appropriate for non-rigid applications, such as textiles, soft surfaces, or highly flexible surfaces. Furthermore, they all exhibit limitations in terms of an overall package of configurability, localization of felt haptic effect, resolution of felt haptic effect, and portability.